Trying to Prove Value of Web Ads

"Consumer Direct is being run in tandem with ACNielsen's Homescan unit, which records the off-line purchases of roughly 60,000 consumer volunteers. About 19,000 of those have also agreed to let Yahoo track their surfing behavior and offer feedback on purchases to Consumer Direct advertisers. From late 2002 through early 2003, Yahoo and Homescan tested marketing campaigns for a handful of companies, including Pepsi and Purina, to see if online ads encouraged consumers to choose those brands of soda and pet food. Buoyed by the initial results, the companies sought out more of the top makers of consumer goods late last year and refined the program."